Methods for reducing flip chip stress

Abstract

Novel methods for reducing shear stress applied to solder bumps on a flip chip. The methods are particularly applicable to reducing temperature-induced shear stress on solder bumps located adjacent to an empty space on a flip chip during high-temperature testing of the chip. According to a first embodiment, the method includes providing an anchoring solder bump in each empty space on the flip chip. The anchoring solder bumps impart additional structural integrity to the flip chip and prevent shear-induced detachment of solder bumps from the flip chip, particularly those solder bumps located adjacent to each anchoring solder bump. According to a second embodiment, the method includes providing an anchoring solder bump in the empty space and then connecting the anchoring solder bump to an adjacent solder bump on the chip using a solder bridge.

1. A method for preventing detachment of functional solder bumps from a flip chip having empty spaces between adjacent ones of the functional solder bumps, comprising the step of:
 stabilizing the functional solder bumps on the flip chip by providing an anchoring solder bump in each of at least a portion of the empty spaces. 
 
   
   
     2. The method of  claim 1  wherein each of said empty spaces has a width of from about 150 um to about 500 um. 
   
   
     3. The method of  claim 1  wherein said providing an anchoring solder bump in at least a portion of the empty spaces comprises the steps of providing an anchoring bump pad in each of the at least a portion of the empty spaces and providing said anchoring solder bump on said anchoring bump pad. 
   
   
     4. The method of  claim 3  wherein each of said empty spaces has a width of from about 150 um to about 500 um. 
   
   
     5. The method of  claim 1  wherein said anchoring solder bump is a material selected from the group consisting of lead, copper, silver and nickel. 
   
   
     6. The method of  claim 5  wherein each of said empty spaces has a width of from typically about 150 um to about 500 um. 
   
   
     7. The method of  claim 5  wherein said providing an anchoring solder bump in at least a portion of the empty spaces comprises the steps of providing an anchoring bump pad in each of the at least a portion of the empty spaces and providing said anchoring solder bump on said anchoring bump pad. 
   
   
     8. The method of  claim 7  wherein each of said empty spaces has a width of from typically about 150 um to about 500 um. 
   
   
     9. The method of  claim 1  further comprising the step of providing a solder bridge between said anchoring solder bump and one of the functional solder bumps. 
   
   
     10. The method of  claim 9  wherein each of said empty spaces has a width of from typically about 150 um to about 500 um. 
   
   
     11. The method of  claim 9  wherein said providing an anchoring solder bump in at least a portion of the empty spaces comprises the steps of providing an anchoring bump pad in each of the at least a portion of the empty spaces and providing said anchoring solder bump on said anchoring bump pad. 
   
   
     12. The method of  claim 9  wherein said anchoring solder bump comprises lead. 
   
   
     13. A method for preventing detachment of functional solder bumps from a flip chip having empty spaces between adjacent ones of the functional solder bumps, comprising the steps of:
 stabilizing the functional solder bumps on the flip chip by providing anchoring solder bumps in at least a portion of the empty spaces, respectively; and 
 providing a printed circuit board substrate on said functional solder bumps and said anchoring solder bumps. 
 
   
   
     14. The method of  claim 13  wherein each of said empty spaces has a width of from typically about 150 um to about 500 um. 
   
   
     15. The method of  claim 13  wherein said providing anchoring solder bumps in at least a portion of the empty spaces, respectively, comprises the steps of providing anchoring bump pads in the at least a portion of the empty spaces, respectively, and providing said anchoring solder bumps on said anchoring bump pads, respectively. 
   
   
     16. The method of  claim 13  wherein each of said anchoring solder bumps comprises lead. 
   
   
     17. A method for preventing detachment of functional solder bumps from a flip chip having empty spaces between adjacent ones of the functional solder bumps, comprising the steps of:
 stabilizing the functional solder bumps on the flip chip by providing anchoring solder bumps in at least a portion of the empty spaces, respectively; 
 providing a solder bridge between each of said anchoring solder bumps and one of the functional solder bumps; and 
 providing a printed circuit board substrate on said functional solder bumps and said anchoring solder bumps. 
 
   
   
     18. The method of  claim 17  wherein each of said empty spaces has a width of from typically about 150 um to about 500 um. 
   
   
     19. The method of  claim 17  wherein said providing anchoring solder bumps in at least a portion of the empty spaces, respectively, comprises the steps of providing anchoring bump pads in the at least a portion of the empty spaces, respectively, and providing said anchoring solder bumps on said anchoring bump pads, respectively. 
   
   
     20. The method of  claim 17  wherein each of said anchoring solder bumps comprises lead.